Display screen or portion thereof with an animated graphical user interface



FIG. 1 is a front view of a first image in a sequence for a display screen or portion thereof with an animated graphical user interface showing the new design; and,

FIG. 2 is a front view of a second image thereof.

The outermost broken line rectangle illustrates a display screen or portion thereof and forms no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-2 . The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with an animated graphical user interface, as shown and described. 